The fact that you work regular hours for the same department does not automatically make you an employee.How long have you worked there?
Been self employed for 25 years.
current work 21 months.
You would only become employed if you have been employed there for more than 4 years when you automatically become an employee.
As such you would only be entitled to payment if the contract you have between you and the estate stipulates that you will be paid if bad weather prevents you from working.
You might be able to get them to give you some money since they must appreciate that you have liabilities to meet but they are not legally obliged to pay you unless the contract says so.
I appreciate that this is not what you wanted to read but an honest opinion is the only one worth having